Nearly half a century ago, Isaiah Berlin delivered an extraordinarily influential lecture called “Two Concepts of Liberty.” The negative concept consists in freedom from—“warding off interference” from external forces. By contrast, the positive concept consists in freedom to—to be “a doer—deciding, not being decided for.” Democracy requires both forms, but current constitutional doctrine adopts an unduly negative approach.

This is especially the case when it comes to political voice. The Supreme Court has resisted attempts to constrain the political impact of money, most notoriously in Citizens United v. Federal Election Commission (2010). But just as telling is Arizona Free Enterprise Club’s Freedom Club PAC v. Bennett (2011), where the Court hobbled the states’ ability to construct public financing systems. Adjusting the funds available to candidates who accept public financing somehow burdens privately financed candidates’ freedom, according to the justices.

The Court’s rationale in campaign finance cases calls on protection of free speech, which invokes a negative concept of liberty because the freedom of speech guaranteed by the First Amendment is largely exercised without government assistance. Political speech, the Court points out, is “an essential mechanism of democracy, for it is the means to hold officials accountable to the people.” True enough.

Yet voting is surely an equally essential mechanism of democracy, and arguably a more direct means for holding officials accountable, but the Court has upheld laws that burden casting a ballot, a positive liberty. In Crawford v. Marion County Election Board (2008), the Court rejected a challenge to an Indiana law requiring already-registered voters to present government-issued photo identification at the polls. (Disclosure: I helped to represent the plaintiffs in the case.) The justices did not agree on every element of the case, but they accepted Indiana’s argument that ID prevents fraud (after recognizing that Indiana could not point to a single example, ever, of impersonation that an ID requirement would have stopped) and enhances “public confidence” in the election process, a rationale the Court has essentially rejected in the political-spending context.

The Court’s strikingly different treatment of burdens on political spending and on voting reflects this positive/negative divide. Effective exercise of the right to vote depends on affirmative government support. A citizen who is handed an official ballot written in a language she does not understand may effectively be denied the right to vote. If the government uses unreliable voting machines or staffs polling places with badly trained workers, citizens may effectively be prevented from voting by the press of other responsibilities that preclude waiting in line for hours. Voter ID laws disenfranchise individuals who find it difficult or impossible to obtain government-issued documents.

A superficial reading of the Constitution might support the Court’s opinions. Although the Constitution is filled with provisions mentioning the “right to vote,” the most explicit protections are phrased almost entirely in negative terms: they prohibit particular forms of disenfranchisement. The Fifteenth and Nineteenth Amendments, for example, forbid denial of the right to vote “on account of race” or “sex”; the Twenty-Fourth, “by reason of failure to pay any poll tax.”

In light of this language, in 1875 the Supreme Court declared itself “unanimously of the opinion that the Constitution of the United States does not confer the right of suffrage upon any one.” To be sure, the equal protection clause provides one important qualification: the government cannot arbitrarily treat voters unequally. This fall a federal court of appeals relied on the clause to hold that if Ohio permitted military voters to cast early ballots the weekend before the November election, it had to make early voting available to other voters on the same terms. But the court was careful to acknowledge that Ohio had not been constitutionally required to offer early voting at all.

As of 2010, more than 5.85 million American citizens were disenfranchised because of criminal convictions.

The consequences of adopting an essentially negative approach to political voice extend beyond enhanced protection for the political deployment of concentrated wealth and beyond new rules, such as voter ID requirements, that block full participation. The negative approach underwrites a practice that continues to set the United States apart among advanced democracies: disenfranchising millions of citizens due to criminal convictions. Even incarcerated prisoners vote in countries as otherwise diverse as the Czech Republic, Denmark, France, Israel, Japan, Kenya, the Netherlands, and Zimbabwe. In the last dozen years, the highest courts of Canada and South Africa and the European Court of Human Rights have each issued opinions recognizing the voting rights of incarcerated citizens.

As of 2010 more than 5.85 million American citizens were disenfranchised as a result of criminal convictions. Only a quarter of those individuals were then incarcerated. Roughly 30 percent were on probation or parole. The remaining 45 percent were ex-offenders, many disenfranchised for life as a result of felony convictions involving small amounts of drugs or nonviolent crimes that never resulted in prison sentences.

Such extensive disenfranchisement would be distressing in any event, but it becomes even more troubling in light of the dramatic effect that offender disenfranchisement has on the black community. More than 2 million African Americans currently are stripped of their right to vote. That’s more than the number of African Americans who gained the franchise in 1870 thanks to the Fifteenth Amendment. Precedent permits offender disenfranchisement unless challengers can show that states adopted or have maintained their practice for purposefully discriminatory reasons, a nearly insurmountable hurdle. In 2005, for example, the Supreme Court refused to review Florida’s lifetime offender disenfranchisement provision even though the ban had been adopted in 1868 precisely for the purpose of disenfranchising newly freed slaves. Lower federal courts acknowledged this unconstitutional motivation but held that the taint somehow had dissipated by 1968, when Florida renewed the ban without giving any reasons for doing so.

Offender disenfranchisement statutes impair the voting rights of people beyond the offenders themselves. Flawed records and negligent purges result in thousands of eligible voters being excluded. More than 2,400 black voters in Florida were erroneously purged before the 2000 election, dwarfing George W. Bush’s 537-vote margin of victory. And punitive offender disenfranchisement statutes deprive the black community as a whole of political power, which in turn skews election results to the right and creates legislative bodies hostile to civil rights and economic justice for the franchised and disenfranchised alike.

Faced with these problems, some activists and scholars suggest the need for a new constitutional amendment recognizing the affirmative right to vote. I think a better approach lies in reviving the late legal scholar Charles Black’s approach to constitutional reasoning. Black argued that the overall structure of the Constitution presupposes free and fair elections in which all qualified citizens can participate. Individual amendments expanding the electorate reflect this general principle. Abolishing poll taxes, for instance, stands for a fundamental commitment to eliminating barriers to registration and to ensuring that wealth is not the means of accessing politics.

And the Court should apply to offender disenfranchisement statutes a principle it has already recognized elsewhere: whether a punishment violates the Eighth Amendment’s bar on cruel and unusual punishment “is judged not by the standards that prevailed in 1685 . . . or when the Bill of Rights was adopted,” but instead by “the evolving standards of decency that mark the progress of a maturing society.”

Today, continuing to disenfranchise millions of our fellow citizens cannot survive that test.